A Bill barring former IRA prisoners from becoming special advisers to Northern Ireland ministers has been delayed.

Hardline unionist Jim Allister needs to consult commissioners who regulate civil service recruitment, and said if debate had progressed on Tuesday there would have been no further opportunity to make adjustments to the draft law.

Sinn Fein has welcomed the suspension of what it claims is a discriminatory measure, introduced at Stormont following a political row over the appointment of a former republican prisoner as adviser to Culture Minister Caral Ni Chuilin.

The legislation was drawn up by the Traditional Unionist Voice (TUV) leader following controversy over Sinn Fein's appointment of Mary McArdle to support the Culture Minister.

She was convicted for her part in the 1984 murder of judge's daughter Mary Travers and the victim's sister Ann protested against the appointment. Ms McArdle subsequently took up a different post in Sinn Fein.

The Bill aims to ban anyone convicted of an offence carrying a jail sentence of five years or more from holding the post of special adviser to a minister.

Former barrister Mr Allister is the only Stormont representative of his party but has support from unionists and the SDLP for the measure. He did not move this stage of his private member's Bill on Tuesday due to an earlier amendment requiring more engagement.

Mr Allister explained that an accepted amendment afforded a role to the Northern Ireland Civil Service Commissioners and said the commission was seeking engagement on resulting issues.

Sinn Fein's Daithi McKay said Mr Allister should not allow anti-republican prejudice to colour his political judgment. He said: "Jim Allister is not requesting suspension of consideration of this Bill because he has all of a sudden accepted the discriminatory nature of it, but because he has no other recourse.

"In his haste to introduce a Bill that was specifically directed at excluding republican political former prisoners from holding positions of influence in the Assembly, he failed to examine the competency of his proposed Bill. The fact that Jim Allister did not check to see if his Bill came under the competency of the Assembly to enact brings into question his political judgment."